The present invention relates to abrasive articles comprised of abrasive particles and polymeric material such as a polymeric reaction product of components comprising saturated polyol, saturated polyisocyanate, and a free radical source.
Abrasive articles comprising abrasive particles coated on and/or dispersed within an organic cellular or foam substrate, (e.g., polyurethane) are well known. Examples of such articles include pads, sheets, discs, and wheels (see, e.g., U.S. Pat. No. 2,780,533 (Hurst), U.S. Pat. No. 2,885,276 (Upton, Jr.), U.S. Pat. No. 2,972,527 (Upton, Jr.), and U.S. Pat. No. 3,252,775 (Tocci-Guilbert). These articles have been employed to abrade a variety of workpieces, including metal and wood. They have also been adapted for abrading operations ranging from coarse dimensioning operations such as xe2x80x9csnaggingxe2x80x9d to fine finishing operations such as polishing and buffing.
Abrasive articles comprising abrasive particles dispersed within and/or adhered to a polyurethane cellular or foam matrix have been used, for example, to impart a final refined surface finish on metal (e.g., steel, stainless steel, aluminum, titanium or titanium alloys) substrates designed for use in any of many applications. In finishing such substrates, what is desired is the ability to repeatedly, from part to part, impart a finish to the metal surface, conform to the design features of the metal surface, and not leave residual abrasive article material (xe2x80x9csmearingxe2x80x9d) on the finished metal surface. Current foam abrasives do not concurrently provide the desired level of each of these features.
The present invention provides abrasive articles (e.g., an abrasive wheel) comprised of abrasive particles and polymeric material. Preferred abrasive articles according to the present invention include abrasive articles comprised of abrasive particles and polymeric reaction product of components comprising saturated polyol, saturated polyisocyanate, and a free radical source (e.g., peroxide).
Abrasive articles according to the present invention also include abrasive articles comprised of abrasive particles and polymeric material comprised of a saturated polyurethane preparable by combining components comprising saturated polyol, saturated polyisocyanate, and a free radical source (e.g., peroxide).
Although not wanting to be bound by theory, it is believed that the polymeric reaction product of isocyanate-functional moieties (with a functionality of 2 or greater) (e.g., a polyisocyanate), with materials reactive with isocyanate-functional moieties, (e.g., hydroxy-functional materials) with a functionality of 2 or greater (e.g., a polyol) is polyurethane. As a general class, term xe2x80x9cpolyurethanexe2x80x9d as used herein includes true polyurethanes, true polyurea, polyurea urethanes, and polyurethane ureas. Isocyanate-functional materials and isocyanate-functional reactive materials vary widely in equivalent weight. Hence, the reaction stoichiometry is based on the isocyanate index (the equivalents of isocyanate functional moieties divided by the equivalents of the isocyanate reactive-functional moieties times one hundred), so that an isocyanate index of 100 means a stoichiometric balance (i.e., that one isocyanate functionality has one isocyanate reactive functionality with which to react). For preferred abrasive articles according to the present invention, there are, by weight, typically 2 parts of free radical source and 20 parts of abrasive particles per hundred parts of the polymeric reaction product of saturated polyol and saturated polyisocyanate.
Preferably, abrasive articles according to the present invention are comprised of a polymeric matrix having voids dispersed throughout. The voids may be isolated (i.e., xe2x80x9cclosed cellxe2x80x9d) and/or intercommunicating (i.e., xe2x80x9copen cellxe2x80x9d). The polymeric matrix may be flexible or rigid. Further, abrasive articles according to the present invention preferably have at least 25 percent void volume, more preferably, at least 50 percent void volume, and even more preferably are in the range from 75 to 90 percent void volume, wherein the percent void volume is a calculated value equal to the difference between the article volume and the sum of the material solids volume fractions of the various components, divided by the article volume, times 100%.
In another aspect, abrasive articles according to the present invention are preferably further comprised of lubricant (e.g., metallic salts of fatty acids, solid lubricants, esters of fatty acids, mineral oils and waxes, and poly(dimethylsiloxane) gum).
In another aspect, the present invention provides a method for making an abrasive article comprising:
combining components comprising saturated polyol, saturated polyisocyanate, a free radical source, and abrasive grains to provide a curable composition; and
curing the curable composition to provide an abrasive article.
In another aspect, the present invention provides a method of abrading a surface, the method comprising:
providing an abrasive article according to the present invention, the abrasive article having an outer surface;
frictionally contacting at least a portion of the outer surface of the abrasive article with a surface of a workpiece; and
moving at least of one the outer surface of the abrasive article or the surface of the workpiece relative to the other to abrade at least a portion of the workpiece surface. The method may include the use of a buffing compound, wherein the buffing compound is on at least a portion of the outer surface of the abrasive article.
Embodiments of abrasive articles according to the present invention are flexible, conformable, and lightweight. Preferred abrasive wheels according to the present invention can be run smoothly and exhibit less xe2x80x9cchatterxe2x80x9d than conventional abrasive wheels. Further, preferred abrasive wheels according to the present invention can utilize less abrasive grain material than conventional abrasive wheels. Preferred abrasive articles according to the present invention also tend not to xe2x80x9csmearxe2x80x9d during use. Smearing, which is typically undesirable, can occur when a workpiece in contact with an abrasive article becomes sufficiently hot such that portions of the abrasive article soften and transfer to the workpiece.